Multiple component solid state white light

ABSTRACT

A white light emitting lamp is disclosed comprising a solid state ultra violet (UV) emitter that emits light in the UV wavelength spectrum. A conversion material is arranged to absorb at least some of the light emitting from the UV emitter and re-emit light at one or more different wavelengths of light. One or more complimentary solid state emitters are included that emit at different wavelengths of light than the UV emitter and the conversion material. The lamp emits a white light combination of light emitted from the complimentary emitters and from the conversion material, with the white light having high efficacy and good color rendering. Other embodiments of white light emitting lamp according to the present invention comprises a solid state laser instead of a UV emitter. A high flux white emitting lamp embodiment according to the invention comprises a large area light emitting diode (LED) that emits light at a first wavelength spectrum and includes a conversion material. A plurality of complimentary solid state emitters surround the large area LED, with each emitter emitting light in a spectrum different from the large area LED and conversion material such that the lamp emits a balanced white light. Scattering particles can be included in each of the embodiments to scatter the light from the emitters, conversion material and complimentary emitters to provide a more uniform emission.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to light emitting diodes (LEDs) and moreparticularly to an apparatus with multiple LEDs that in combinationproduce white light.

[0003] 2. Description of the Related Art

[0004] Light emitting diodes (LEDs) are an important class ofsolid-state devices that convert electric energy to light. Theygenerally comprise an active layer of semiconductor material sandwichedbetween two oppositely doped layers. When a bias is applied across thedoped layers, holes and electrons are injected into the active layerwhere they recombine to generate light. Light is emittedomnidirectionally from the active layer and from all surfaces of theLED. Recent advances in LEDs (such as nitride based LEDs) have resultedin highly efficient light sources that surpass the efficiency offilament-based light sources, providing light with equal or greaterbrightness in relation to input power.

[0005] One disadvantage of conventional LEDs used for lightingapplications is that they cannot generate white light from their activelayers. One way to produce white light from conventional LEDs is tocombine different wavelengths of light from different LEDs. For example,white light can be produced by combining the light from red, green andblue emitting LEDs, or combining the light from blue and yellow LEDs.

[0006] One disadvantage of this approach is that it requires the use ofmultiple LEDs to produce a single color of light, increasing the overallcost and complexity. In addition, the different colors of light areoften generated from different types of LEDs fabricated from differentmaterial systems. Combining different LED types to form a white lamp canrequire costly fabrication techniques and can require complex controlcircuitry since each device may have different electrical requirementsand may behave differently under varied operating conditions (e.g. withtemperature, current or time).

[0007] More recently, the light from a single blue emitting LED has beenconverted to white light by surrounding the LED with a yellow phosphor,polymer or dye, with a typical phosphor being cerium-doped yttriumaluminum garnet (Ce:YAG). [See Nichia Corp. white LED, Part No.NSPW300BS, NSPW312BS, etc.; See also U.S. Pat. No. 5,959,316 to Hayden,“Multiple Encapsulation of Phosphor-LED Devices”]. The surroundingphosphor material “downconverts” the wavelength of at least some of theLED light, changing its color. For example, if a nitride-based blueemitting LED is surrounded by a yellow phosphor, some of the blue lightpasses through the phosphor without being changed while a substantialportion of the remaining light is downconverted to yellow. The LED willthus emit both blue and yellow light, which combine to provide a whitelight.

[0008] This approach has been successfully used to commercialize whiteLEDs for a variety of applications such as flashlights, indicatorlights, display backlighting, and architectural lighting. However,conventional blue LEDs are too dim for many general lightingapplications that currently make use of filament-based or fluorescentlamps. While improvements in blue LED efficiency and output power wouldbe beneficial in increasing the light output from white LEDs, a numberof other factors exist which limit the performance of such devices. Forexample, phosphor materials have a finite conversion efficiency,resulting in “conversion loss” since a portion of the absorbed light isnot re-emitted as downconverted light. Additionally, each time a higherenergy (e.g., blue) photon is converted to a lower energy (e.g., yellow)photon, light energy is lost (Stokes loss), resulting in an overalldecrease in white LED efficiency. This reduction in efficiency increasesas the gap between the wavelengths of the absorbed and re-emitted(downconverted) light increases. Finally, for blue LEDs to emit anoutput light flux sufficient for room illumination, the LED chipsthemselves can become very hot, causing damage the component devicelayers of the LED chip itself, or degrading surrounding encapsulation ordownconverting media.

[0009] Another disadvantage of the above white light emitterarrangements (red+green+blue LEDs or blue LEDs combined with yellowphosphors) is that they do not produce the optimal spectral emissionnecessary for both high efficacy and high color rendering. Simulationsof white emitters show that high efficacy and color rendering can beachieved with an output light spectrum consisting of spectrally narrowemission in the blue and red regions, with a slightly broader emissionin the green region.

[0010] In the case of the red+green+blue LED lamps, the spectralemission lines of the component LEDs are typically narrow (e.g. 10-30 nmfull width at half maximum (FWHM)). While it is possible to achievefairly high values of efficacy and color rendering with this approach,wavelength ranges exist in which it is difficult to obtainhigh-efficiency LEDs (e.g. approximately 550 nm). As a result, it isdifficult to achieve both high efficacy and high color rendering indexwith low manufacturing cost and high yield. This can be particularlyproblematic when spectral requirements call for high efficiency greenLEDs, since such LEDs have only been realized in the (In, Ga, Al)Nsystem and are typically subject to low yield and strong wavelength andemission variations with operating conditions such as drive current andtemperature. While more simplified white lamps may be realized usingonly two LEDs emitting at complimentary colors (e.g. blue, yellow), itis exceedingly difficult to achieve high color rendering coefficients insuch lamps, primarily due to the lack of any red light in the resultingspectrum.

[0011] In the case of blue LEDs combined with yellow phosphor, theresulting white light is produced without a red light source. Since theresulting light is typically deficient in one of the primary colors,lamps fabricated in this manner display poor color rendering.

[0012] The desired spectrum can be more closely achieved using acombination of a blue LED with two separate phosphors emitting in thegreen and red spectral regions, or using an ultra violet LED with red,green and blue phosphors. However, suitable red phosphors having highconversion efficiency and the desired excitation and emissioncharacteristics have yet to be reported. Even if such red phosphors wereavailable, they would be subject to significant energy (Stokes) lossesdue to the conversion of high energy blue or UV photons to lower energyred photons.

[0013] Patent Publication No. US 2002/0070681 A1 to Shimizu discloses anLED lamp exhibiting a spectrum closer to the desired spectrum. The lamphas a blue LED for producing a blue wavelength light, a red emittingLED, and a phosphor which is photoexcited by the emission of the blueLED to exhibit luminescence having an emission spectrum wavelengthbetween the blue and red wavelength spectrum. The phosphor is preferablya yellow or green emitting phosphor and in the embodiments shown, thephosphor covers both the red and blue LEDs.

[0014] One of the disadvantages of the Shimizu lamp is that blue LEDsare not as efficient as other LEDs emitting at other wavelengthspectrums and a limited number of phosphors are available forluminescence from a blue wavelength of light. Another disadvantage isthat with red and blue LEDs placed side by side, the projected light mayhave an asymmetric appearance such that the light appears red on oneside and blue on the other. Since phosphor particles typically must beon the order of at least a few microns diameter to achieve highconversion efficiency (i.e., much larger than the wavelength of blue oryellow light) and particles which are larger than the wavelength oflight are poor scatterers, covering one or both of the LEDs withphosphor generally does not adequately scatter the LED light to combinethe different wavelengths. This can be a particular problem with largearea LEDs used for high power, high output.

[0015] Another disadvantage of a number of the embodiments disclosed inShimizu is that they show blue and red LEDs placed on top of one anotherand then covered by the phosphor. This can result in the shorterwavelength blue light being absorbed by the component device layers(e.g., active layers, metallization layers) of the red LED device,thereby decreasing the overall efficiency of the lamp. Also, by coveringthe red LED with phosphor some of the phosphor particles may absorb someof the red light, which can result in a loss of efficiency because it isgenerally not possible to “up-convert” the absorbed red light to higherenergy green light in an efficient manner.

[0016] Shimizu also discloses an optical lens as part of its lamp, withthe inside surface of the lens being roughened to increase mixing of theLED light. Such approaches are generally not effective and can decreaseefficiency by interfering with the purpose of the lens, which is toreduce backscattering of light at the lens/air interface and possiblesubsequent re-absorption within the body of the lamp or LED.

[0017] Solid-state semiconductor lasers convert electrical energy tolight in much the same way as LEDs. They are structurally similar toLEDs but include mirrors on two opposing surfaces, one of which ispartially transmissive. In the case of edge emitting lasers, the mirrorsare on the side surfaces; the mirrors provide optical feedback so thatstimulated emission can occur. This stimulated emission provides ahighly collimated/coherent light source. A vertical cavity laser worksmuch the same as an edge emitting laser but the mirrors are on the topand the bottom. It provides a similar collimated output from its topsurface. Some types of solid-state lasers can be more efficient thanLEDs at converting electrical current to light.

SUMMARY OF THE INVENTION

[0018] The present invention seeks to provide solid-state white emittinglamps with high efficacy and good color rendering. One embodiment of awhite light emitting lamp according to the present invention comprises asolid state ultra violet (UV) emitter (e.g., laser or LED) that emitslight in the UV wavelength spectrum. A conversion material is arrangedto absorb at least some of the light emitting from the UV emitter andre-emit light at one or more different wavelengths of light. One or morecomplimentary solid-state emitters are included that emit wavelengthspectrums of light that are different than the UV emitter and theconversion material. The lamp emits a white light combination of lightemitted from the complimentary emitters and from the conversionmaterial, with the white light having high efficacy and good colorrendering.

[0019] A second embodiment of white light emitting lamp according to thepresent invention comprises a solid-state laser emitting light in afirst wavelength spectrum. A conversion material is arranged to absorbat least some of the light emitting from the laser and re-emits light atone or more different wavelength spectrums of light. One or morecomplimentary solid-state emitters are included that emit wavelengths oflight different than the laser and the conversion material. The lampemits a white light combination of light emitted from the laser,complimentary emitters, and conversion material, the white light havinghigh efficacy and good color rendering. The lamp may also incorporatevarious optics or scattering materials/surfaces to promote mixing anddispersion or mixing and focusing of the component light colors.

[0020] Another embodiment of a white light emitting lamp according tothe present invention comprises a first solid state emitter that emitslight in a first wavelength spectrum. A conversion material is includedto absorb at least some of the light from the first solid-state emitterand emit light at one or more different wavelength spectrums. One ormore complimentary emitters are included with each emitting light at awavelength spectrum different from said first wavelength spectrum andsaid conversion material wavelength spectrums. Scattering elements (suchas particles, microviods, etc.) are arranged to scatter the light fromthe first emitter, conversion material and complimentary emitters. Thelamp emits a uniform white light combination of light from the firstemitter, conversion material and complimentary emitters.

[0021] An embodiment of a high flux white emitting lamp according to thepresent invention comprises a large area light emitting diode (LED) thatemits light at a first wavelength spectrum. A conversion material isarranged to absorb at least some of the light from the large area LEDand re-emit at least one wavelength light in a spectrum different fromthe first wavelength spectrum. A plurality of complimentary solid-stateemitters surround the large area LED, with each emitter emitting lightin a spectrum different from the large area LED and conversion material.The lamp emits a balanced and uniform white light combination of lightfrom the large area LED, conversion material and complimentary emitters.The white light also has high efficacy and good color rendering.

[0022] One embodiment of a method for producing white light with highefficacy and good color rendering according to the present inventioncomprises generating light in the UV wavelength spectrum and passing theUV light through a conversion material that absorbs the UV light andre-emits light at one or more different wavelength spectrums. The methodfurther comprises generating complimentary light at one or morewavelength spectrums, each of which is different from the conversionmaterial wavelength spectrums. The conversion material light and thecomplimentary light are combined to generate white light with highefficacy and good color rendering.

[0023] Another method for producing white light with high efficacy andgood color rendering, comprises generating laser light that is passedthrough a conversion material that absorbs at least some of the laserlight and re-emits light at one or more different wavelength spectrums.The method further comprises generating complimentary light at one ormore wavelength spectrums that is different from the wavelength spectrumfor the conversion material light and combining the conversion materiallight and said complimentary light to generate white light with highefficacy and good color rendering.

[0024] These and other further features and advantages of the inventionwill be apparent to those skilled in the art from the following detaileddescription, taken together with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a sectional view of one embodiment of a lamp accordingto the present invention comprising a red LED, a UV LED, and conversionmaterial covering the UV LED;

[0026]FIG. 2 is a sectional view of another embodiment of a lampaccording to the present invention that is similar to the lamp in FIG.1, with the conversion material also covers the red LED;

[0027]FIG. 3 is a sectional view of another embodiment of a lampaccording to the present invention comprising a green LED, red LED, UVLED, and conversion material covering the UV LED;

[0028]FIG. 4 is a sectional view of another embodiment of a lampaccording to the present invention that is similar to the lamp in FIG.3, with the conversion material covering all of the LEDs;

[0029]FIG. 5 is a sectional view of another embodiment of another lampaccording to the present invention comprising a blue LED, red LED, UVLED, and conversion material covering the UV LED;

[0030]FIG. 6 is a sectional view of another embodiment of a lampaccording to the invention that is similar to the lamp in FIG. 5, withthe conversion material covering all of the LEDs;

[0031]FIG. 7 is a sectional view of another embodiment of a lampaccording to the present invention, with a red LED, blue laser andconversion material covering the blue laser;

[0032]FIG. 8 is a sectional view of another embodiment of a lampaccording to the present invention that is similar to the lamp in FIG.7, with a different conversion material covering the blue laser;

[0033]FIG. 9 is a sectional view of another embodiment of a lampaccording to the present invention that is similar to the lamp in FIG. 7or 8, with the conversion material also covering the red LED;

[0034]FIG. 10 is a sectional view of another embodiment of a lampaccording to the present invention comprising blue LEDs covered by ayellow conversion material and two red lasers;

[0035]FIG. 11 is a plan view of another embodiment of a lamp accordingto the present invention comprising a large area LED surrounded bycomplementary LEDs;

[0036]FIG. 12 is a sectional view of the lamp in FIG. 11, taken alongsection lines 12-12;

[0037]FIG. 13 is a sectional view of another embodiment of a whiteemitting lamp according to the present invention comprising scatteringparticles in its conversion material;

[0038]FIG. 14 is a sectional view of another embodiment of a lampaccording to the present invention comprising scattering particles inits epoxy;

[0039]FIG. 15 is a sectional view of another embodiment of a lampaccording to the present invention comprising a layer of scatteringparticles; and

[0040]FIG. 16 is a sectional view of another embodiment of a lampaccording to the present invention comprising a clear/transparentmaterial between the emitters and conversion material.

DETAILED DESCRIPTION OF THE INVENTION

[0041] White Lamp Using UV Emitters

[0042]FIG. 1 shows one embodiment of a multi-component solid-state lampwhite lamp 10 constructed in accordance with the invention. It comprisesa first light emitter 12 that emits in the ultraviolet wavelengthspectrum. Alternatively, the first light emitter 12 can emit light inother “short” wavelength spectrums. The emitter 12 is preferably a lightemitting diode (LED), but it can also be other emitters, such as asolid-state laser or organic light emitting diode. The lamp 10 furthercomprises a complimentary second light emitter 14 that emits in the redwavelength spectrum and is also preferably a LED, but can also be asolid-state laser or organic light emitting diode.

[0043] The details of operation and fabrication of conventional LEDs areknown and are only briefly discussed. Conventional LEDs can befabricated from a number of material systems by known methods, with asuitable method being fabrication by Metal Organic Chemical VaporDeposition (MOCVD). LEDs typically have an active layer sandwichedbetween two oppositely doped layers that are either doped p-type orn-type. The top layer of the LED is usually p-type and bottom layer 13is usually n-type, although LEDs also work if the layers are reversed.The p-type and n-type layers have respective contacts that each have alead to apply a bias across p- and n-type layers. This bias results inthe active layer emitting light omnidirectionally. The entire LED can begrown on a substrate.

[0044] The first and second LEDs 12, 14 are mounted on a submount 16 formechanical stability. The submount 16 can also contain electricalcircuitry for controlling the relative amount of current or powerapplied to the respective LEDs 12, 14, or to otherwise modify theelectric signal applied to the LEDs 12, 14. The submount 16 can alsocontain components and circuitry to make the lamp resistant toelectrostatic shock. Depending on the particular embodiment, one or bothof the LEDs 12, 14 can be in electrical contact with the submount 16.The submount 16 is mounted at the horizontal base 17 of “metal cup” 18that typically has conductive paths (not shown) for applying a biasacross the contacts on the LEDs 12, 14, to cause each of the LEDs toemit light.

[0045] The bias can either be applied directly to the LEDs along theconductive paths or it can be applied to the LEDs fully or partiallythrough the submount 16 and its electronic circuitry. The cup 18 canhave a reflective surface 20 that reflects light emitted from the LEDs12,14 so that it contributes to the light emitted from the lamp 10.

[0046] The lamp 10 further comprises a conversion material 22 thatsurrounds the first UV emitter 12 except for the surface of the emitter12 that is adjacent to the submount. The material 22 can be one or moreflourescent or phosphorescent material such as a phosphor, flourescentdye or photoluminescent semiconductor. The material 22 absorbs at leastsome of the electromagnetic radiation (light) emitted by the UV LED 12and re-emits at least some of the absorbed radiation at one or morewavelength spectrums that are different from the absorbed wavelength. Inthe case of the UV emitter 12, the conversion material 22 has acombination of materials that absorb UV light and re-emit light in thegreen and blue wavelength spectrums. Different materials can be used forabsorbing the UV light and re-emitting green light, with a preferredmaterial being a Sr:thiogallate phosphor. Different materials can alsobe used for absorbing UV light and re-emitting blue light, with apreferred material being ZnS or BaMgAl₁₀O₁₇ doped with appropriateimpurities. The LEDs 12,14, submount 16, and conversion material 22 canbe encased in and protected by a clear epoxy 24 that fills the metal cup16.

[0047] When the appropriate electrical signal is applied to the lamp 10,the UV and red LEDs 12, 14, emit light at their respectivecharacteristic spectrum. At least some of the UV light is absorbed bythe conversion material 22 and re-emitted as green and blue light. Thecombination of blue, green light from the conversion material, and redlight from the red LED, provides white light with high efficacy andcolor rendering that appears white when viewed by the human eye.

[0048] The lamp 10 shows the combination of a blue and green light beingre-emitted from the conversion material, but in an alternativeembodiment according to the present invention, a yellow emittingphosphor can be used instead of green. A full range of broad yellowspectral emission is possible using phosphors based on the (Gd, Y)₃(Al,Ga)₅O₁₂:Ce system. These phosphors are stable and typically display highconversion efficiency when excited using UV light. The combination oflight from these phosphors, along with light from the blue emittingphosphor and red LED provide a versatile white lamp with high efficacyand high color rendering.

[0049] Using a UV emitter 12 with a conversion material 22 to convert UVto blue/green or blue/yellow light has a number of advantages. Higherefficiency UV emitters are available compared to blue or green emittersand in the case of solid-state lasers, short wavelength lasers are moreeasily achieved than blue lasers. Also, a wider variety of highefficiency phosphors are available which can be excited by shortwavelength radiation (250-400 nm).

[0050]FIG. 2 shows another embodiment of a solid state white lamp 30according to the present invention. It has the same submount 16, firstUV LED 12, second red LED 14, metal cup 18 and epoxy 24. However, thelamp 30 has a conversion material 32 that covers both the UV and redLEDs 12, 14, with the conversion material absorbing the UV light andre-emitting in the blue and green wavelength spectrum. Most of the lightemitted by the red LED is not absorbed by the conversion material, andpasses through to contribute to emission by the lamp 30.

[0051] To maximize the uniformity of the overall emission from the lamp30 (color as a function of viewing angle) the UV and red LEDs 12, 14 canbe placed as close together as practical. By covering both the LEDs 12,14 with the conversion material 32, the manufacturing problems andreduced yield associated with covering only one LED, can be avoided.However, covering the red LED with the conversion material may result insome of the red light being absorbed as it passes through the conversionmaterial.

[0052]FIGS. 3 and 4 show additional embodiments of a lamp 40, 60,according to the present invention, with each of the lamps having a UVemitter 42, used in combination with complimentary green and redemitters 44, 46. The emitters are preferably LEDs, although otherdevices can also be used. Each of the LEDs 42, 44, 46 is mounted on asubmount 48 similar to the submount 16 in FIGS. 1 and 2, and in eachembodiment the submount 48 is mounted at the base of a metal cup 50 thatis similar to the metal cup 18 in FIGS. 1 and 2. The cup 50 includesconductive paths (not shown) for applying a bias across the LEDs 42, 44,46, to cause each of them to emit light. The bias can either be applieddirectly to the emitters or can be applied through the submount 48 andits electronic circuitry. The lamps 40 and 60 can also be encased in anepoxy 54 that fills the cup 50 to cover and protect the lamp components.

[0053] With the appropriate signal applied to the lamp 40 in FIG. 4, theLEDs 42, 44, 46 produce light at their respective wavelength spectrum.The UV emitter 42 is covered by a blue conversion material 52 made ofZnS or BaMgAl₁₀O₁₇ doped with appropriate impurities or another suitableblue-converting material, such that at least some of the UV light fromthe UV emitter 42 is absorbed by the conversion material 52 andre-emitted as blue light. The lamp 40 simultaneously radiates blue,green and red light, which combine to produce a white light having highefficacy and high color rendering.

[0054] In the lamp 60 of FIG. 4, all of the LEDs 42, 44, 46 are coveredby the blue conversion material 56. Light from the UV LED 42 is absorbedby the conversion material 56 and re-emitted as blue light. Most of thelight from the green and red LEDs 44, 46 passes through the conversionmaterial 56 without being absorbed, such that the lamp 60 emits a whitecombination of the blue, green and red light.

[0055]FIGS. 5 and 6 show additional embodiments of a lamp 70, 90,according to the present invention, with each having a UV emitter 72,used in combination with a blue emitter 74 and a red emitter 76. Each ofthe emitters 72, 74, 76 is preferably an LED and each is mounted on asubmount 78 similar to the submount 16 in FIGS. 1 and 2. In eachembodiment the submount 78 is mounted at the base of a metal cup 80 thatis similar to the cup 18 in FIGS. 1 and 2. Conductive paths (not shown)are included for applying a bias across the LEDs 72, 74, 76, to causeeach of them to emit light. Each of the lamps also includes a clearepoxy 82 to cover and protect the lamp components.

[0056] In lamp 70, the UV LED 72 is covered by a conversion material 84(e.g. thiogallate phosphor) that absorbs UV light and re-emits greenlight. In lamp 90 a similar conversion material 86 covers the UV LED 72and also covers the red and blue LEDs 74, 76. For lamps 70, 90 the LEDs72, 74, 76 emit in their respective wavelength spectrums when a bias isapplied and the UV wavelength light from each UV LED 72 is absorbed bythe respective conversion material 84, 86 and re-emitted as green light.In lamp 70 the green light combines with the direct light from the blueand green emitters 74, 76. In lamp 90 the green light combines with theblue and red light that passes through the conversion material 86. Ineither case, the lamps 70, 90 emit a white light combination of red,blue and green.

[0057] Depending on the application of each of the lamp embodimentsdescribed above, it may be desirable to arrange the particularconversion material such that it absorbs essentially all of the UV lightfrom its particular UV emitter. UV light is not useful for illuminationand at certain intensity levels can be harmful to eyes or skin.

[0058] In the embodiments above a single LED is shown for each type ofLED, but the optimal arrangement may require a plurality of LEDs of oneor both types. Further, the LEDs shown can have larger or smalleremission areas.

[0059] Solid State Laser Emitters

[0060]FIG. 7 shows another embodiment of a lamp 100 according to thepresent invention. It comprises a solid-state laser 102 and acomplimentary second emitter 106 that are both mounted to a submount 108similar to the submounts described above. Conductive paths can beincluded to apply a bias across the laser 102 and second emitter 106,and the device can then be mounted to the bottom of a metal cup 110,filled with epoxy. A conversion material 104 is included that covers thelaser 102 and absorbs blue light and re-emits in a different wavelengthspectrum than the light from the laser 102.

[0061] For the lamp 100, the laser 102 preferably emits blue wavelengthspectrum, although other types of lasers can be used. The conversionmaterial 104 is preferably made of a material that absorbs blue lightand re-emits green light. The emitter 106 is preferably a LED that emitsin the red light spectrum. When a bias is applied across the laser 102and the LED 106, the laser 102 emits in the blue light wavelengthspectrum and a suitable amount of conversion material 104 is included sothat less than all of the blue light is absorbed by the conversionmaterial 104 and some of the blue light passes through. The red LED 106emits red light and the conversion material 104 re-emits green lightsuch that the lamp 100 emits a white light combination of the red, greenand blue light, with high efficacy and good color rendering.

[0062] Lasers have the advantage of emitting a coherent light sourcethat can be selectively scattered or directed. As lasers are furtherdeveloped they may become preferable over LEDs, because they have thepotential for higher efficiency and higher output than LEDs.

[0063]FIG. 8 shows another lamp 120 according to the present inventionthat is similar to the lamp 100 in FIG. 7. It includes a blue emittinglaser 122 and a red emitter 124 that is preferably a LED. The laser 122and red LED 124 are mounted to a submount 123, and the submount 123 canthen be mounted to the bottom of a metal cup 128. In lamp 120, the bluelaser 122 is covered by a yellow conversion material 130 that absorbsblue light and re-emits yellow light. When the laser 122 and red LED 124are emitting, the yellow conversion material 130 absorbs some of theblue light and emits yellow light such that the lamp 100 emits a whitelight combination of blue, yellow and red light having good efficacy andcolor rendering.

[0064] For each of the embodiments described, the conversion materialcan cover the laser and complimentary LED. For instance, FIG. 9 showsanother embodiment of a lamp 140 according to the present invention thatincludes a blue emitting laser 142 and a red emitting LED 144 mounted ona submount 146. A conversion material 148 covers the laser 142 and thered LED 144. The conversion material 148 contains material that absorbssome of the lasers blue light and re-emits green (or yellow). Most ofthe light from the red LED 144 passes through the conversion material148 such that the lamp 140 emits a white light combination of blue,green (or yellow) and red light.

[0065] Many different types of lasers and LEDs can be used that emit indifferent wavelength spectrums. Many different combinations of laserembodiments of lamps according to the present invention can be realizedwith many different numbers of lasers or LEDs. For example, FIG. 10shows another embodiment of a similar lamp 150 according to the presentinvention having two blue emitting LEDs 152 between two red solid-statelasers 154. The blue LEDs 152 are covered by a conversion material 156that absorbs blue light and re-emits green light. As the LEDs 152 andlasers 154 emit light, the conversion material absorbs some of the bluelight such that the lamp 150 emits a white light combination of blue,green and red light. In an alternative embodiment (not shown), theconversion material 156 covers the blue LEDs 152 and the red lasers 154.Alternatively, blue LEDs may be combined with red lasers, with at leastsome of the light emitted from the blue laser converted to light ofanother wavelength by a downconverting media according to the presentinvention.

[0066] Large Area Emitters Combined With Multiple Emitters

[0067] The prior art lamps, as well as some of the lamps describedabove, can produce a projected light that can have an asymmetricappearance. For instance, lamp embodiments with a blue emitter,conversion material, and red emitter, can appear as though the projectedlight is more red on one side and more blue on the other.

[0068] This is a particular problem with large area LEDs that are usefulfor high-power, high output lamps. Higher current levels can be appliedto larger LEDs which results in higher luminous flux. Multiple largearea LEDs can be used in solid-state lamps that can operate at highpower levels up to 5-70 Watts and beyond. When complimentary LEDs areplaced side by side to the large area LED, the lamp tends to producewhite light that is not balanced.

[0069] To help provide a more symmetric appearance to the projectedlight, multiple complimentary LEDs can be used to surround each largearea LED (or to surround a group of large area LEDs) such that the highluminous flux of the large area LED is balanced by the surrounding LEDs.This type of arrangement in a single package can also provide advantagesin heat sinking, compactness and color mixing.

[0070] To illustrate this arrangement, FIGS. 11 and 12 show a lamp 160according to the present invention having a large area LED 162surrounded by a plurality of complimentary LEDs 164. The LEDs aremounted to a submount 166, which can then be mounted to the base of ametal cup 167. Many different large area LEDs can be used, with asuitable large area LED 164 being a blue emitting LED. A conversionmaterial 168 covers the LED 162 with the preferred conversion material168 absorbing the blue light and re-emitting yellow light. In anotherembodiment of the lamp 160, the conversion material 168 absorbs bluelight and re-emits green light. The surrounding LEDs 164 emit red lightand are spaced around the LED 162 in a sufficient number to provide abalance to the high flux of the LED 162 such that the lamp emits abalanced white light. The lamp 160 has four surrounding LEDs 164 aroundthe large area LED 162, but a different number of surrounding LEDs 164can be used depending on the intensity of the large area LED 162, andthe size and intensity of the surrounding LEDs 164. When the large areaLED 162 and surrounding LEDs 164 are emitting, the lamp 160 emits abalanced white light combination of the blue, green and red light.

[0071] Similar to the embodiments above, the components of the lamp 160can be encased in epoxy 169 and the submount 166 and/or metal cup 167can have conductors to apply a bias to the LEDs 162, 164. Also, inalternative embodiments of the lamp 160, the conversion material cancover all the LEDs 162, 164 and different colors of LED 162, 164 can beused.

[0072] Scattering Particles

[0073] To improve the uniformity of light emitting from the lampsdescribed above, it can be desirable to scatter the light as it emitsfrom the various emitters. One way to scatter light is by usingscattering particles that randomly refract light. To effectively scatterlight, the diameter of these particles should be approximately one halfof the wavelength of the light being scattered. In air, this wouldresult in the particles being approximately 0.2 to 0.25 microns indiameter and the diameters would be smaller if the particles are in amedium having a different index of refraction than air such as epoxy.

[0074] In the lamps described above, a conversion material typicallysurrounds at least one of the emitters and typically comprises phosphorparticles. The conversion efficiency of phosphors generally decreases asthe size of the phosphor particles decrease. As a result, it isdifficult to obtain high conversion efficiency phosphors particles thatare smaller than approximately 1 micron in diameter, making phosphorparticles generally too large to effectively scatter light.

[0075] To produce more uniform light emission in white emitting lampsdescribed above (and prior art lamps) scattering particles can beincluded such that light from the emitters passes through them and isrefracted to mix the light and provide an overall light emission that ismore uniform in color and intensity. The scattering particles can bearranged in different locations, such as in the conversion material orepoxy, or the particles can form their own layer. The preferredscattering particles would not substantially absorb light at any of thewavelengths involved and would have a substantially different index ofrefraction than the material in which it is embedded (for example,epoxy) The scattering particles should have as high of an index ofrefraction as possible. Suitable scattering particles can be made oftitanium oxide (TiO₂) which has a high index of refraction (n=2.6 to2.9) and is effective at scattering light. Since the primary requirementfor the scattering “particles” is that they have a different index ofrefraction from their surrounding material and that they have aparticular size range, other elements such as small voids or pores couldalso be used as “scattering particles”.

[0076]FIG. 13 shows one embodiment of a lamp 170, according to thepresent invention, having a UV emitting LED 172 and red emitting LED 174mounted on a submount 176 along with the necessary conductive paths. Aconversion material 178 is included that covers both the UV and red LEDs172, 174 such that light from the LEDs passes through the conversionmaterial 178. The conversion material 178 contains scattering particles180 disposed to refract the light passing through the conversionmaterial 178. Each of the scattering particles 180 can be similarlysized so that they primarily scatter a single wavelength of light, suchas from the UV LED 72, or they can have different sizes to scatter lightof different wavelengths of light, such as from the LEDs 172, 174 andthe conversion material 178. Like the embodiments above, the LEDs 172,174, conversion material 178, and submount 176 are in a metal cup 182and are encased in an epoxy 184.

[0077]FIGS. 14 and 15 show two additional embodiments of a lamp 190,200, according to the present invention. Each lamp 190, 200 has a UV andred LED 172, 174, a submount 176, and a conversion material 178, all ofwhich are in a metal cup 182 and epoxy 184. However, for lamp 190, thescattering particles 192 are disposed in the epoxy 184. For lamp 200,the scattering particles 194 are formed in a layer on top of the epoxy184. The light from the LEDs 172, 174 and conversion material 176 passesthrough the scattering particles 192, 194 where different wavelengths oflight can be refracted depending on the size and material of theparticles 192, 194. Like the lamp 170 in FIG. 13, the scatteringparticles 192, 194 can be similarly sized or can have different sizesdepending on the wavelength of light emitted from the LEDs 172, 174 andthe conversion material 176.

[0078] Miscellaneous Features

[0079] Other lamp features according to the present invention canimprove light extraction from the lamps described above. FIG. 16 showsanother embodiment of a lamp 210 according to the present inventionhaving a clear material 212, such as an epoxy, arranged over theemitters 214, 216, which in this embodiment are UV and red emitting LEDsrespectively. The material 212 preferably forms a hemispheric volumewith the LED 212, 216 as close as practical to the origin of thehemisphere. The hemisphere should have a large radius compared to thedimensions of the LEDs. The material 212 preferably has an index ofrefraction approximately the same as the primary surfaces of the LEDs214, 216 from which most of the light is emitted (e.g. the substrate forflip-chip LEDs or the top surface for a standard LED). A layer ofconversion material 218 is then included on the surface of the clearlayer 212. This arrangement minimizes reflection of light at theinterface between the LED surfaces and the clear layer 212, and theclear layer 122 and layer of conversion material 218, back into the LEDactive layers where the light can be absorbed.

[0080] In the lamp embodiments according to the present invention, theintensities of the individual LEDs (and lasers) can be controlled. Thiscan be accomplished by controlling the relative emission of the LEDsthrough control of the applied current, and controlling the blue/greenemission of the conversion material by controlling the amount andlocation of the conversion material. This type of control allows thelamps to emit at color points not accessible using the blue LED/yellowphosphor approach. This control/adjustability could also enhancemanufacturing yield by selecting and matching the emissioncharacteristics of the different LEDs (peak emission wavelength, etc.),thereby allowing the fabrication of lamps having very tight spectraldistribution (color, hue, etc.) over a large range of color temperature.Similarly, by controlling the relative power applied to the respectiveLEDs or the amount of phosphor applied, a large range of flexibility isavailable both for providing the desired chromaticity and controllingthe color output of the individual devices. A lamp according to theinvention could be provided that allows the end user to control therelative powers applied to the respective LEDs. The lamp could be“tuned” by the user to achieve desired colors or hues from a singlelamp. This type of control can be provided by known control electronics.

[0081] The lamps according to the present invention can also includelenses and facets to control the direction of the lamp's emitting light.Other components could be added related to thermal management, opticalcontrol, or electrical signal modification and control, to further adaptthe lamps to a variety of applications.

[0082] Although the present invention has been described in considerabledetail with reference to certain preferred configurations thereof, otherversions are possible. As mentioned above, different LEDs that emit atdifferent colors can be used in embodiments described above. In thoseembodiments where one emitter is described as providing light in aparticular wavelength spectrum, two or more emitters can be used. Theconversion materials described above can use many different types ofmaterial that absorb different wavelengths of light and re-emitdifferent wavelengths beyond those described above. Therefore, thespirit and scope of the appended claims should not be limited to theirpreferred versions contained therein.

1. A white light emitting lamp, comprising: a solid state ultra violet(UV) emitter emitting light in the UV wavelength spectrum; a conversionmaterial arranged to absorb at least some of the light emitting fromsaid UV emitter and re-emit light at one or more different wavelengthspectrums of light; and one or more complimentary solid state emittersemitting different wavelength spectrums of light than said UV emitterand said conversion material, said lamp emitting a white lightcombination of light emitted from said complimentary emitters and fromsaid conversion material, said white light having high efficacy and goodcolor rendering; said UV and complimentary emitters being mounted in areflector element having conductors to apply a bias to said emitters,said bias causing said emitters to emit light.
 2. The lamp of claim 1,wherein said UV emitter comprises a UV emitting light emitting diode(LED), said conversion material absorbs at least some of the lightemitting from said UV LED and re-emits wavelengths of light in the blueand green spectrum.
 3. The lamp of claim 1, wherein said one or morecomplimentary emitters comprise a LED emitting a wavelength of light inthe red spectrum.
 4. The lamp of claim 1, wherein, said UV emittercomprises a UV emitting LED and said conversion material absorbs atleast some of the light emitting from said UV LED and re-emitswavelengths of light in the blue spectrum.
 5. The lamp of claim 1,wherein said one or more complimentary emitters comprise a LED emittinga wavelength of light in the green spectrum and a LED emitting awavelength of light in the red spectrum.
 6. The lamp of claim 1, whereinsaid UV emitter comprises a UV emitting LED and said conversion materialabsorbs at least some of the light emitting from said UV LED andre-emits wavelengths of light in the green spectrum.
 7. The lamp ofclaim 1, wherein said one or more complimentary emitters comprises a LEDemitting a wavelength of light in the green spectrum and a LED emittinga wavelength of in the red spectrum.
 8. The lamp of claim 1,wherein-said conversion material covers both said UV emitter and saidone or more complimentary emitters, most of the light from saidcomplimentary emitters passing through said conversion material withoutbeing absorbed.
 9. The lamp of claim 1, wherein said UV andcomplimentary emitters are mounted on a submount.
 10. (Canceled)
 11. Thelamp of claim 1, wherein said UV and complimentary emitters eachcomprise an emitter from the group consisting of an LED, a solid statelaser, and organic light emitting diode.
 12. The lamp of claim 1,further comprising scattering particles arranged to scatter the lightfrom said UV and complimentary emitters to produce a substantiallyuniform emission of white light from said lamp, said scatteringparticles each having a diameter of approximately one half a wavelengthof light emitted by either said UV emitter or said complimentaryemitters.
 13. (Canceled)
 14. The lamp of claim 1, further comprising alayer of clear material between said UV emitter and said conversionmaterial, said clear layer forming a hemispheric or sheet volume. 15.The lamp of claim 14, wherein said layer of clear material has an indexof refraction approximately the same as that of the emitting surface ofsaid UV emitter.
 16. The lamp of claim 1, wherein the intensities of thelight emitted from said UV emitter and complimentary emitters can beindependently varied to vary the color or hue of white light emittedfrom said lamp.
 17. The lamp of claim 1, further comprising a componentto control the direction of light emitted from said lamp.
 18. The lampof claim 1, wherein said conversion material comprises a material fromthe group consisting of a phosphor, fluorescent dye, photoluminescentsemiconductor, and combinations thereof.
 19. The lamp of claim 1,wherein said conversion material absorbs substantially all the lightemitting from said UV emitter.
 20. The lamp of claim 1, wherein said UVemitter comprises a plurality of large area LED and said complimentaryemitters comprise a plurality of LEDs surrounding said large area LED,said lamp emitting a balanced white light.
 21. A white light emittinglamp, comprising: a solid state laser emitting light in a firstwavelength spectrum; a conversion material arranged to absorb at leastsome of the light emitting from said laser and re-emit light at one ormore different wavelength spectrums of light; and one or morecomplimentary solid state emitters emitting different wavelengths oflight than said laser and said conversion material, said lamp emitting awhite light combination of light emitted from said laser, complimentaryemitters, and conversion material, said white light having high efficacyand good color rendering; said laser emitting light in the bluewavelength spectrum, said conversion material absorbing some of thelight emitting from said laser and re-emitting a wavelength of light inthe green spectrum, the non-absorbed blue light passing through saidconversion material.
 22. (Canceled)
 23. (Canceled)
 24. The lamp of claim21, wherein said one or more complimentary emitters comprise a LEDemitting a wavelength of light in the red spectrum.
 25. The lamp ofclaim 21, wherein said conversion material absorbs some of the lightemitting from said laser and re-emits a wavelength of light in the blueand yellow spectrum, the non-absorbed blue light passing through saidconversion material.
 26. The lamp of claim 21, further comprising asubmount and metal cup, said laser and complimentary emitters mounted onsaid submount and said submount mounted in said reflector element. 27.The lamp of claim 21, further comprising scattering particles arrangedto scatter the light from said laser and complimentary emitters toproduce a more uniform emission of white light from said lamp.
 28. Thelamp of claim 21, wherein the intensities of the light emitted from saidlaser and complimentary emitters can be independently varied to vary thecolor or hue of white light emitted from said lamp.
 29. The lamp ofclaim 21, wherein said conversion material comprises a material from thegroup consisting of a phosphor, fluorescent dye, photoluminescentsemiconductor, and combinations thereof.
 30. A white light emittinglamp, comprising: a first solid state emitter emitting light in a firstwavelength spectrum; a conversion material to absorb at least some ofthe light from said first solid state emitter, and emit light at one ormore different wavelength spectrums; one or more complimentary emitterseach of which emits light at a wavelength spectrum different from saidfirst wavelength spectrum and said conversion material wavelengthspectrums; and scattering particles arranged to scatter the light fromsaid first emitter, conversion material and complimentary emitters, saidlamp emitting a uniform white light combination of light from said firstemitter, conversion material and complimentary emitters; said scatteringparticles each having a diameter of approximately one half a wavelengthof light emitted by either said first emitter, conversion material orcomplimentary emitters.
 31. (Canceled)
 32. The lamp of claim 30, whereinsaid scattering particles are disposed within said conversion material.33. The lamp of claim 30, further comprising a clear encapsulantmaterial, said encapsulant encasing at least part of said lamp with atleast some of the light from said first emitter, conversion material andcomplimentary emitters passing through said encapsulant, said scatteringparticles disposed within said encapsulant.
 34. The lamp of claim 30,wherein said scattering particles form a layer of scattering particleswith at least some of the light from said first emitter, conversionmaterial and complimentary emitters passing through said layer.
 35. Thelamp of claim 30, wherein the white light emitted by said lamp has highefficacy and good color rendering.
 36. A high flux white emitting lamp,comprising: a large area light emitting diode (LED) emitting light at afirst wavelength spectrum; a conversion material arranged to absorb atleast some of the light from said large area LED, and re-emit at leastone wavelength light in a spectrum different from said first wavelengthspectrum; and a plurality of complimentary solid state emitterssurrounding said large area LED and each emitting light in a spectrumdifferent from said large area LED and said conversion material, saidlamp emitting a balanced and uniform white light combination of lightfrom said large area LED, conversion material and complimentaryemitters, said white light having high efficacy and good colorrendering; said conversion material covering both said large area LEDand said plurality of complimentary emitters, most of the light fromsaid complimentary emitters passing through said conversion materialwithout being absorbed.
 37. (Canceled)
 38. The lamp of claim 36, furthercomprising a submount and reflector element, said large area LED andcomplimentary emitters mounted on said submount and said submountmounted in said metal cup.
 39. The lamp of claim 36, further comprisingscattering particles arranged to scatter the light from said large areaLED and complimentary emitters to produce a substantially uniformemission of white light from said lamp.
 40. The lamp of claim 36,wherein the intensities of the light emitted from said large area LEDand complimentary emitters can be independently varied to vary the coloror hue of white light emitted from said lamp.
 41. The lamp of claim 36,wherein said large area LED comprises a plurality of large area LEDs.42. A method for producing white light with high efficacy and good colorrendering, comprising: generating light in the UV wavelength spectrum;passing said UV light through a conversion material that absorbs said UVlight and re-emits light at one or more different wavelength spectrums;generating complimentary light at one or more wavelength spectrums thatis different from said conversion material wavelength spectrums;combining said conversion material light and said complimentary light togenerate white light with high efficacy and good color rendering; andproviding reflective element that reflects said UV light, complimentarylight and conversion material light such that all contribute to lightemission direction, said reflective element also comprising a means forcausing said light generation.
 43. The method of claim 42, furthercomprising scattering said conversion material light and saidcomplimentary light to generate substantially uniform white light.
 44. Amethod for producing white light with high efficacy and good colorrendering, comprising: generating laser light; passing said laser lightthrough a conversion material that absorbs at least some of said laserlight and re-emits light at one or more different wavelength spectrums;generating complimentary light at one or more wavelength spectrums thatis different from said conversion material wavelength spectrums; andcombining said conversion material light and said complimentary light togenerate white light with high efficacy and good color rendering, saidlaser light being blue light, said conversion material absorbing some ofthe light emitting from said laser and re-emitting a wavelength of lightin the green spectrum, the non-absorbed blue light passing through saidconversion material.